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کامپیوتر و شبکه::
جریان کد
Specifically, the scheme has four modules: (1) a train uses its on-board sensors to obtain its speed, location, and RSSI (Received Signal Strength Indicator) of train-trackside WiFi channel; (2) the train reports these real-time measurements to the railway control center with the legacy GSM-R networks; (3) according to the measurements, the control center or its WiFi AP adaptively customizes the protected codestream bitrate and AP-train handover time; (4) the train renders the received codestream which passes the authenticity verification process.
As shown in the performance analysis, the present scheme ensures the codestream authenticity and provides high QoS (Quality of Service) in the lossy subway WiFi environment.
However, since a video codestream delivered over wireless channel is usually erroneous in subway environments [2]-[4], most of subway
In the proposed scheme, an operation center creates a trusted SVC (Scalable Video Code) codestream, broadcasts it to all the APs on the subway lines.
According to the measured train location, speed and WiFi signal quality, each AP adaptively tunes WiFi bitrate and optimally truncates codestream such that the passing-by trains can receive the video of high quality in real-time.
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